OK, let's work through this together. We're starting with 390 and we're going to multiply it by 410, which means we add 390 to itself 410 times.
Step 1: 0 + 390 = 390
Step 2: 390 + 390 = 780
Step 3: 780 + 390 = 1170
Step 4: 1170 + 390 = 1560
Step 5: 1560 + 390 = 1950
Step 6: 1950 + 390 = 2340
Step 7: 2340 + 390 = 2730
Step 8: 2730 + 390 = 3120
Step 9: 3120 + 390 = 3510
Step 10: 3510 + 390 = 3900
Step 11: 3900 + 390 = 4290
Step 12: 4290 + 390 = 4680
Step 13: 4680 + 390 = 5070
Step 14: 5070 + 390 = 5460
Step 15: 5460 + 390 = 5850
Step 16: 5850 + 390 = 6240
Step 17: 6240 + 390 = 6630
Step 18: 6630 + 390 = 7020
Step 19: 7020 + 390 = 7410
Step 20: 7410 + 390 = 7800
Step 21: 7800 + 390 = 8190
Step 22: 8190 + 390 = 8580
Step 23: 8580 + 390 = 8970
Step 24: 8970 + 390 = 9360
Step 25: 9360 + 390 = 9750
Step 26: 9750 + 390 = 10140
Step 27: 10140 + 390 = 10530
Step 28: 10530 + 390 = 10920
Step 29: 10920 + 390 = 11310
Step 30: 11310 + 390 = 11700
Step 31: 11700 + 390 = 12090
Step 32: 12090 + 390 = 12480
Step 33: 12480 + 390 = 12870
Step 34: 12870 + 390 = 13260
Step 35: 13260 + 390 = 13650
Step 36: 13650 + 390 = 14040
Step 37: 14040 + 390 = 14430
Step 38: 14430 + 390 = 14820
Step 39: 14820 + 390 = 15210
Step 40: 15210 + 390 = 15600
Step 41: 15600 + 390 = 15990
Step 42: 15990 + 390 = 16380
Step 43: 16380 + 390 = 16770
Step 44: 16770 + 390 = 17160
Step 45: 17160 + 390 = 17550
Step 46: 17550 + 390 = 17940
Step 47: 17940 + 390 = 18330
Step 48: 18330 + 390 = 18720
Step 49: 18720 + 390 = 19110
Step 50: 19110 + 390 = 19500
Step 51: 19500 + 390 = 19890
Step 52: 19890 + 390 = 20280
Step 53: 20280 + 390 = 20670
Step 54: 20670 + 390 = 21060
Step 55: 21060 + 390 = 21450
Step 56: 21450 + 390 = 21840
Step 57: 21840 + 390 = 22230
Step 58: 22230 + 390 = 22620
Step 59: 22620 + 390 = 23010
Step 60: 23010 + 390 = 23400
Step 61: 23400 + 390 = 23790
Step 62: 23790 + 390 = 24180
Step 63: 24180 + 390 = 24570
Step 64: 24570 + 390 = 24960
Step 65: 24960 + 390 = 25350
Step 66: 25350 + 390 = 25740
Step 67: 25740 + 390 = 26130
Step 68: 26130 + 390 = 26520
Step 69: 26520 + 390 = 26910
Step 70: 26910 + 390 = 27300
Step 71: 27300 + 390 = 27690
Step 72: 27690 + 390 = 28080
Step 73: 28080 + 390 = 28470
Step 74: 28470 + 390 = 28860
Step 75: 28860 + 390 = 29250
Step 76: 29250 + 390 = 29640
Step 77: 29640 + 390 = 30030
Step 78: 30030 + 390 = 30420
Step 79: 30420 + 390 = 30810
Step 80: 30810 + 390 = 31200
Step 81: 31200 + 390 = 31590
Step 82: 31590 + 390 = 31980
Step 83: 31980 + 390 = 32370
Step 84: 32370 + 390 = 32760
Step 85: 32760 + 390 = 33150
Step 86: 33150 + 390 = 33540
Step 87: 33540 + 390 = 33930
Step 88: 33930 + 390 = 34320
Step 89: 34320 + 390 = 34710
Step 90: 34710 + 390 = 35100
Step 91: 35100 + 390 = 35490
Step 92: 35490 + 390 = 35880
Step 93: 35880 + 390 = 36270
Step 94: 36270 + 390 = 36660
Step 95: 36660 + 390 = 37050
Step 96: 37050 + 390 = 37440
Step 97: 37440 + 390 = 37830
Step 98: 37830 + 390 = 38220
Step 99: 38220 + 390 = 38610
Step 100: 38610 + 390 = 39000
Step 101: 39000 + 390 = 39390
Step 102: 39390 + 390 = 39780
Step 103: 39780 + 390 = 40170
Step 104: 40170 + 390 = 40560
Step 105: 40560 + 390 = 40950
Step 106: 40950 + 390 = 41340
Step 107: 41340 + 390 = 41730
Step 108: 41730 + 390 = 42120
Step 109: 42120 + 390 = 42510
Step 110: 42510 + 390 = 42900
Step 111: 42900 + 390 = 43290
Step 112: 43290 + 390 = 43680
Step 113: 43680 + 390 = 44070
Step 114: 44070 + 390 = 44460
Step 115: 44460 + 390 = 44850
Step 116: 44850 + 390 = 45240
Step 117: 45240 + 390 = 45630
Step 118: 45630 + 390 = 46020
Step 119: 46020 + 390 = 46410
Step 120: 46410 + 390 = 46800
Step 121: 46800 + 390 = 47190
Step 122: 47190 + 390 = 47580
Step 123: 47580 + 390 = 47970
Step 124: 47970 + 390 = 48360
Step 125: 48360 + 390 = 48750
Step 126: 48750 + 390 = 49140
Step 127: 49140 + 390 = 49530
Step 128: 49530 + 390 = 49920
Step 129: 49920 + 390 = 50310
Step 130: 50310 + 390 = 50700
Step 131: 50700 + 390 = 51090
Step 132: 51090 + 390 = 51480
Step 133: 51480 + 390 = 51870
Step 134: 51870 + 390 = 52260
Step 135: 52260 + 390 = 52650
Step 136: 52650 + 390 = 53040
Step 137: 53040 + 390 = 53430
Step 138: 53430 + 390 = 53820
Step 139: 53820 + 390 = 54210
Step 140: 54210 + 390 = 54600
Step 141: 54600 + 390 = 54990
Step 142: 54990 + 390 = 55380
Step 143: 55380 + 390 = 55770
Step 144: 55770 + 390 = 56160
Step 145: 56160 + 390 = 56550
Step 146: 56550 + 390 = 56940
Step 147: 56940 + 390 = 57330
Step 148: 57330 + 390 = 57720
Step 149: 57720 + 390 = 58110
Step 150: 58110 + 390 = 58500
Step 151: 58500 + 390 = 58890
Step 152: 58890 + 390 = 59280
Step 153: 59280 + 390 = 59670
Step 154: 59670 + 390 = 60060
Step 155: 60060 + 390 = 60450
Step 156: 60450 + 390 = 60840
Step 157: 60840 + 390 = 61230
Step 158: 61230 + 390 = 61620
Step 159: 61620 + 390 = 62010
Step 160: 62010 + 390 = 62400
Step 161: 62400 + 390 = 62790
Step 162: 62790 + 390 = 63180
Step 163: 63180 + 390 = 63570
Step 164: 63570 + 390 = 63960
Step 165: 63960 + 390 = 64350
Step 166: 64350 + 390 = 64740
Step 167: 64740 + 390 = 65130
Step 168: 65130 + 390 = 65520
Step 169: 65520 + 390 = 65910
Step 170: 65910 + 390 = 66300
Step 171: 66300 + 390 = 66690
Step 172: 66690 + 390 = 67080
Step 173: 67080 + 390 = 67470
Step 174: 67470 + 390 = 67860
Step 175: 67860 + 390 = 68250
Step 176: 68250 + 390 = 68640
Step 177: 68640 + 390 = 69030
Step 178: 69030 + 390 = 69420
Step 179: 69420 + 390 = 69810
Step 180: 69810 + 390 = 70200
Step 181: 70200 + 390 = 70590
Step 182: 70590 + 390 = 70980
Step 183: 70980 + 390 = 71370
Step 184: 71370 + 390 = 71760
Step 185: 71760 + 390 = 72150
Step 186: 72150 + 390 = 72540
Step 187: 72540 + 390 = 72930
Step 188: 72930 + 390 = 73320
Step 189: 73320 + 390 = 73710
Step 190: 73710 + 390 = 74100
Step 191: 74100 + 390 = 74490
Step 192: 74490 + 390 = 74880
Step 193: 74880 + 390 = 75270
Step 194: 75270 + 390 = 75660
Step 195: 75660 + 390 = 76050
Step 196: 76050 + 390 = 76440
Step 197: 76440 + 390 = 76830
Step 198: 76830 + 390 = 77220
Step 199: 77220 + 390 = 77610
Step 200: 77610 + 390 = 78000
Step 201: 78000 + 390 = 78390
Step 202: 78390 + 390 = 78780
Step 203: 78780 + 390 = 79170
Step 204: 79170 + 390 = 79560
Step 205: 79560 + 390 = 79950
Step 206: 79950 + 390 = 80340
Step 207: 80340 + 390 = 80730
Step 208: 80730 + 390 = 81120
Step 209: 81120 + 390 = 81510
Step 210: 81510 + 390 = 81900
Step 211: 81900 + 390 = 82290
Step 212: 82290 + 390 = 82680
Step 213: 82680 + 390 = 83070
Step 214: 83070 + 390 = 83460
Step 215: 83460 + 390 = 83850
Step 216: 83850 + 390 = 84240
Step 217: 84240 + 390 = 84630
Step 218: 84630 + 390 = 85020
Step 219: 85020 + 390 = 85410
Step 220: 85410 + 390 = 85800
Step 221: 85800 + 390 = 86190
Step 222: 86190 + 390 = 86580
Step 223: 86580 + 390 = 86970
Step 224: 86970 + 390 = 87360
Step 225: 87360 + 390 = 87750
Step 226: 87750 + 390 = 88140
Step 227: 88140 + 390 = 88530
Step 228: 88530 + 390 = 88920
Step 229: 88920 + 390 = 89310
Step 230: 89310 + 390 = 89700
Step 231: 89700 + 390 = 90090
Step 232: 90090 + 390 = 90480
Step 233: 90480 + 390 = 90870
Step 234: 90870 + 390 = 91260
Step 235: 91260 + 390 = 91650
Step 236: 91650 + 390 = 92040
Step 237: 92040 + 390 = 92430
Step 238: 92430 + 390 = 92820
Step 239: 92820 + 390 = 93210
Step 240: 93210 + 390 = 93600
Step 241: 93600 + 390 = 93990
Step 242: 93990 + 390 = 94380
Step 243: 94380 + 390 = 94770
Step 244: 94770 + 390 = 95160
Step 245: 95160 + 390 = 95550
Step 246: 95550 + 390 = 95940
Step 247: 95940 + 390 = 96330
Step 248: 96330 + 390 = 96720
Step 249: 96720 + 390 = 97110
Step 250: 97110 + 390 = 97500
Step 251: 97500 + 390 = 97890
Step 252: 97890 + 390 = 98280
Step 253: 98280 + 390 = 98670
Step 254: 98670 + 390 = 99060
Step 255: 99060 + 390 = 99450
Step 256: 99450 + 390 = 99840
Step 257: 99840 + 390 = 100230
Step 258: 100230 + 390 = 100620
Step 259: 100620 + 390 = 101010
Step 260: 101010 + 390 = 101400
Step 261: 101400 + 390 = 101790
Step 262: 101790 + 390 = 102180
Step 263: 102180 + 390 = 102570
Step 264: 102570 + 390 = 102960
Step 265: 102960 + 390 = 103350
Step 266: 103350 + 390 = 103740
Step 267: 103740 + 390 = 104130
Step 268: 104130 + 390 = 104520
Step 269: 104520 + 390 = 104910
Step 270: 104910 + 390 = 105300
Step 271: 105300 + 390 = 105690
Step 272: 105690 + 390 = 106080
Step 273: 106080 + 390 = 106470
Step 274: 106470 + 390 = 106860
Step 275: 106860 + 390 = 107250
Step 276: 107250 + 390 = 107640
Step 277: 107640 + 390 = 108030
Step 278: 108030 + 390 = 108420
Step 279: 108420 + 390 = 108810
Step 280: 108810 + 390 = 109200
Step 281: 109200 + 390 = 109590
Step 282: 109590 + 390 = 109980
Step 283: 109980 + 390 = 110370
Step 284: 110370 + 390 = 110760
Step 285: 110760 + 390 = 111150
Step 286: 111150 + 390 = 111540
Step 287: 111540 + 390 = 111930
Step 288: 111930 + 390 = 112320
Step 289: 112320 + 390 = 112710
Step 290: 112710 + 390 = 113100
Step 291: 113100 + 390 = 113490
Step 292: 113490 + 390 = 113880
Step 293: 113880 + 390 = 114270
Step 294: 114270 + 390 = 114660
Step 295: 114660 + 390 = 115050
Step 296: 115050 + 390 = 115440
Step 297: 115440 + 390 = 115830
Step 298: 115830 + 390 = 116220
Step 299: 116220 + 390 = 116610
Step 300: 116610 + 390 = 117000
Step 301: 117000 + 390 = 117390
Step 302: 117390 + 390 = 117780
Step 303: 117780 + 390 = 118170
Step 304: 118170 + 390 = 118560
Step 305: 118560 + 390 = 118950
Step 306: 118950 + 390 = 119340
Step 307: 119340 + 390 = 119730
Step 308: 119730 + 390 = 120120
Step 309: 120120 + 390 = 120510
Step 310: 120510 + 390 = 120900
Step 311: 120900 + 390 = 121290
Step 312: 121290 + 390 = 121680
Step 313: 121680 + 390 = 122070
Step 314: 122070 + 390 = 122460
Step 315: 122460 + 390 = 122850
Step 316: 122850 + 390 = 123240
Step 317: 123240 + 390 = 123630
Step 318: 123630 + 390 = 124020
Step 319: 124020 + 390 = 124410
Step 320: 124410 + 390 = 124800
Step 321: 124800 + 390 = 125190
Step 322: 125190 + 390 = 125580
Step 323: 125580 + 390 = 125970
Step 324: 125970 + 390 = 126360
Step 325: 126360 + 390 = 126750
Step 326: 126750 + 390 = 127140
Step 327: 127140 + 390 = 127530
Step 328: 127530 + 390 = 127920
Step 329: 127920 + 390 = 128310
Step 330: 128310 + 390 = 128700
Step 331: 128700 + 390 = 129090
Step 332: 129090 + 390 = 129480
Step 333: 129480 + 390 = 129870
Step 334: 129870 + 390 = 130260
Step 335: 130260 + 390 = 130650
Step 336: 130650 + 390 = 131040
Step 337: 131040 + 390 = 131430
Step 338: 131430 + 390 = 131820
Step 339: 131820 + 390 = 132210
Step 340: 132210 + 390 = 132600
Step 341: 132600 + 390 = 132990
Step 342: 132990 + 390 = 133380
Step 343: 133380 + 390 = 133770
Step 344: 133770 + 390 = 134160
Step 345: 134160 + 390 = 134550
Step 346: 134550 + 390 = 134940
Step 347: 134940 + 390 = 135330
Step 348: 135330 + 390 = 135720
Step 349: 135720 + 390 = 136110
Step 350: 136110 + 390 = 136500
Step 351: 136500 + 390 = 136890
Step 352: 136890 + 390 = 137280
Step 353: 137280 + 390 = 137670
Step 354: 137670 + 390 = 138060
Step 355: 138060 + 390 = 138450
Step 356: 138450 + 390 = 138840
Step 357: 138840 + 390 = 139230
Step 358: 139230 + 390 = 139620
Step 359: 139620 + 390 = 140010
Step 360: 140010 + 390 = 140400
Step 361: 140400 + 390 = 140790
Step 362: 140790 + 390 = 141180
Step 363: 141180 + 390 = 141570
Step 364: 141570 + 390 = 141960
Step 365: 141960 + 390 = 142350
Step 366: 142350 + 390 = 142740
Step 367: 142740 + 390 = 143130
Step 368: 143130 + 390 = 143520
Step 369: 143520 + 390 = 143910
Step 370: 143910 + 390 = 144300
Step 371: 144300 + 390 = 144690
Step 372: 144690 + 390 = 145080
Step 373: 145080 + 390 = 145470
Step 374: 145470 + 390 = 145860
Step 375: 145860 + 390 = 146250
Step 376: 146250 + 390 = 146640
Step 377: 146640 + 390 = 147030
Step 378: 147030 + 390 = 147420
Step 379: 147420 + 390 = 147810
Step 380: 147810 + 390 = 148200
Step 381: 148200 + 390 = 148590
Step 382: 148590 + 390 = 148980
Step 383: 148980 + 390 = 149370
Step 384: 149370 + 390 = 149760
Step 385: 149760 + 390 = 150150
Step 386: 150150 + 390 = 150540
Step 387: 150540 + 390 = 150930
Step 388: 150930 + 390 = 151320
Step 389: 151320 + 390 = 151710
Step 390: 151710 + 390 = 152100
Step 391: 152100 + 390 = 152490
Step 392: 152490 + 390 = 152880
Step 393: 152880 + 390 = 153270
Step 394: 153270 + 390 = 153660
Step 395: 153660 + 390 = 154050
Step 396: 154050 + 390 = 154440
Step 397: 154440 + 390 = 154830
Step 398: 154830 + 390 = 155220
Step 399: 155220 + 390 = 155610
Step 400: 155610 + 390 = 156000
Step 401: 156000 + 390 = 156390
Step 402: 156390 + 390 = 156780
Step 403: 156780 + 390 = 157170
Step 404: 157170 + 390 = 157560
Step 405: 157560 + 390 = 157950
Step 406: 157950 + 390 = 158340
Step 407: 158340 + 390 = 158730
Step 408: 158730 + 390 = 159120
Step 409: 159120 + 390 = 159510
Step 410: 159510 + 390 = 159900

So, 390*410 = 159900